1. Field of the Invention
The present invention relates to a power supply apparatus and, more particularly, to a power supply apparatus using a fuel cell as power source.
2. Description of the Related Art
Along with the advancement of information society, the number of people using mobile devices is increasing. In many cases, power supply voltage required by such mobile devices differ for each device. When the mobile device is connected with an external power source, the voltage of the external power source needs to be adjusted to that capable of driving the device. A technique is proposed where a voltage instructing device is so provided between the external power source and the mobile device that the voltage is easily adjusted. Information on the voltage capable of driving the corresponding mobile device is stored beforehand in this voltage instructing device. The voltage instructing device sends this information to the external power source. Thereby, the external power source can detect the voltage required by the mobile device and adjust an output voltage therefor.
However, when this technique using the voltage instructing device is implemented, a plurality of corresponding voltage instructing devices need to be prepared for the mobile devices, respectively. This may not be convenient for users. Also, where a fuel cell is used as the external power source, variation in output power makes it difficult to operate the mobile devices stably.